1. Field of the Invention
The present invention is directed to low methoxyl pectins that display pseudoplasticity and no phase separation in aqueous solution comprising at least one polyvalent cation, and processes for producing the same. In particular, the present invention is directed to low methoxyl pectins prepared from non-calcium sensitive pectins. The present invention is also directed to processes for suspending particulates using low methoxyl pectins prepared from pectins which are not sensitive to polyvalent cations such as calcium, and in particular using low methoxyl pectins prepared from non-calcium sensitive pectins (NCSP). Furthermore, the present invention relates to stabilizing particles in aqueous systems containing low methoxyl pectins prepared from non-calcium sensitive pectins.
2. Background of the Invention and Related Art
The problem encountered with drinks containing insoluble components, such as pulps, clouds, insoluble particles, essential oils, and the like, is the tendency of the insoluble components to separate, e.g., via sedimentation or creaming.
In order to maintain insoluble components in suspension, xanthan has been added to fruity drinks to raise the viscosity or alter the rheology of the drink. Xanthan, when added to aqueous solutions even at low concentrations, also exhibits very strong pseudoplasticity and pseudoplasticity at low concentration without any evidence of thixotropy. However, xanthan results in negative organoleptic perception (undesirable mouth-feel) in beverages. Thus, there is a need to provide a suspension aid that has the desired particle suspension properties of xanthan without the undesired mouth-feel.
Alginates and pectins have also been used in beverages in an attempt to suspend insoluble particles. Alginates and pectins, however, tend to undergo syneresis or phase separation during long term storage. Attempts have been made to use pectins as suspension aids with reduced syneresis properties. Pectins are complex polysaccharides having exposed reactive carboxylic acid moieties. More specifically, pectins are composed primarily of D-galacturonic acid, interrupted with sugars such as L-rhamnose. The D-galacturonic acid subunits have reactive sites. In the presence of a polyvalent cation, such as calcium (Ca2++), the acid moieties or reactive sites of dissolved pectin form a bridge across the calcium with the acid moieties from other nearby pectin molecules, forming a gelatinous mass.
Pectin is available as either a low methoxyl pectin (LMP) or high methoxyl pectin (HMP). Low methoxyl pectin has a degree of esterification (DE) of less than about 50% and is highly reactive with cations. High methoxyl pectin has a DE of greater than about 50% and is less reactive with polyvalent cations such as calcium.
The term xe2x80x9cdegree of esterificationxe2x80x9d is intended to mean the extent to which free carboxylic acid groups contained in the polygalacturonic acid chain of the pectin have been esterified (e.g., by methylation) or in other ways rendered non-acidic (e.g., by amidation).
The structure of the pectin, in particular the DE, dictates many of the resultant physical and/or chemical properties of the pectin. Pectin gelation also depends on the soluble-solids content, the pH and calcium ion concentration. With respect to the latter, it is believed that the calcium ions form complexes with free carboxyl groups, particularly those on LMP.
Pectin, as first extracted, has a relatively high degree of esterification of about 70-75%. Such pectin is ideal for use in jam and jellies. However, other uses require the preparation of pectins with different setting characteristics. This can be accomplished by modifying pectin to reduce the degree of esterification. One common process for achieving this is an acid hydrolysis. Alternative processes are directed to the use of alkali at low temperatures, ammonia, or purified pectin esterase.
During deesterification, the ester groups on the pectin can be removed in a random or blockwise manner. When the ester groups are removed from any galacturonic acid residues chemically or when using very specific enzymes, deesterification can occur in a xe2x80x9crandom manner.xe2x80x9d When the ester groups are removed either at non-reducing ends or next to free carboxyl groups by a single-chain mechanism, they are referred to as being deesterified in a xe2x80x9cblockwise manner,xe2x80x9d as blocks of unesterified galacturonic acid units are created. The unesterified galacturonic acid units formed by blockwise deesterification are highly reactive to polyvalent cations. Pectins having such blocks are said to be xe2x80x9ccalcium sensitive.xe2x80x9d
Pectins that have been reduced to low methoxyl pectins can gel in the presence of polyvalent cations. Calcium is the most common source of polyvalent cations for food gel applications. Gelation is due to the formations of intermolecular junction zones between homogalacturonic acid units. Because of the electrostatic nature of the bonds, pectins gels are very sensitive to conditions which can modify the environment of the carboxyl groups through which the calcium ion is linked to a neighboring pectin molecule. The gel forming ability of pectin increases with decreasing DE, and low or high methoxyl pectins with blockwise distribution of free carboxyl groups are very sensitive to low calcium levels. As the number and size of blocks along the pectin backbone increase, the sensitivity to calcium increases. However, a typical problem associated with the increasing sensitivity of a pectin to calcium is an increased tendency for the pectin to pre-gel and to display syneresis.
Amidation also increases the gelling ability of low methoxyl pectins. Amidated pectins require less calcium to gel and are less prone to precipitation at elevated calcium levels. Amide groups along the pectin backbone associate through hydrogen bonding allowing gelation at lower calcium levels.
Attempts have been made in the industry to use pectin as a suspending aid. For example, U.S. Pat. No. 5,866,190 issued to Barey discloses compositions for stabilizing a non-milk drink containing insoluble components comprising a pectin and alginate. The pectin of Barey can be amidated or non-amidated HMPs and LMPs. These compositions, however, display high levels of syneresis. It is also essential that the pectin/alginate mixture be dissolved in aqueous medium in the absence of free calcium ions or that a calcium complexing agent be used. The complexing agent is added either to the pectin/alginate solution or to the fruit juice.
EP 0 664 300 A1, and U.S. application Ser. No. 08/161,635 now U.S. Pat. No. 6,143,346 and Ser. No. 08/890,983, now U.S. Pat. No. 6,207,194to Glahn disclose the use of pectin as a suspension aid in foodstuffs, personal hygienic devices, and in cosmetics. The pectin of Glahn, however, displays an increased tendency to form gels which show high levels of syneresis.
The pectin of Glahn is HMP containing two fractions, a calcium sensitive pectin (CSP) and a non-calcium sensitive pectin (NSCP). xe2x80x9cNon-calcium sensitive pectinxe2x80x9d fraction refers to a fraction having a lower degree of calcium sensitivity. xe2x80x9cCalcium sensitive pectinxe2x80x9d fraction refers to a fraction having a higher degree of calcium sensitivity. xe2x80x9cCalcium sensitivityxe2x80x9d is intended to mean the ability of pectin to become viscous in solution by the addition of calcium.
Typically, commercial low methoxyl conventional (LMC) and low methoxyl amidated pectins are prepared from the unfractionated pectin (containing CSP and NCSP as disclosed in Glahn). Random deesterification by chemical methods and/or enzymatic processes is typically used to prepare low methoxyl pectin from an unfractionated pectin precursor. The resulting pectin is a mixture of low DE CSP with carboxyl blocks of increased size and number with a low DE NCSP fraction with completely random carboxyl distribution. These pectins with larger and more numerous carboxyl blocks are more sensitive to calcium, and thus display an increased tendency to form gels which show high levels of syneresis.
In view of the above, there is an existing need for a pectin suspension aid that has shear thinning behavior for use in aqueous food, cosmetic, and pharmaceutical products.
There is also an existing need for a pectin to produce a stable aqueous system with shear thinning behavior (pseudoplasticity) and acceptable mouth-feel for use as a particle suspending aid. A xe2x80x9cstable aqueous systemxe2x80x9d refers to an aqueous system that can maintain stable viscosity at rest or under controlled shear conditions. xe2x80x9cStable viscosityxe2x80x9d or xe2x80x9cstabilityxe2x80x9d refers to the maintenance of the insoluble components in suspension and the homogeneity of the suspension initially formed. Rheologically this is often referred to as high, low shear viscosity or pseudoplasticity. Stability also means that the rheology of the aqueous system is stable for a time period of at least one to twelve months or longer.
In addition, there is also an existing need for a pectin that does not undergo syneresis upon storage or form a separate gel phase even in the presence of relatively high levels of calcium such as 250 mM.
In view of the foregoing, one aspect of the invention is directed to low methoxyl pectins that display pseudoplasticity and no phase separation in an aqueous solution comprising at least one polyvalent cation, and are prepared from non-calcium sensitive pectins. The present invention is also directed to processes for producing low methoxyl pectins prepared from non-calcium sensitive pectins.
The present invention also relates to processes for suspending insoluble components in an aqueous system using low methoxyl pectins that display pseudoplasticity and no phase separation. The present invention is still further directed to stabilizing particles in aqueous systems containing low methoxyl pectins prepared from non-calcium sensitive pectins.
The low methoxyl pectin of the present invention preferably has a degree of esterification from about 20 to 50%, and more preferably from about 24 to 40%.
The molecular weight of the low methoxyl pectin of the present invention is preferably from about 60 to 150 kDalton, and more preferably from about 80 to 100 kDalton.
At a shear rate of about 0.04 sxe2x88x921cPs, the low methoxyl pectin of the present invention preferably has a viscosity of at least about 300 cPs, and more preferably from about 800 to 1,200 cPs.
At a shear rate of about 50 sxe2x88x921cPs, the viscosity of the low methoxyl pectin of the present invention is preferably from about 1 to 20 cPs, and more preferably from about 2 to 10 cPs.
At a shear rate of about 100 sxe2x88x921cPs, the low methoxyl pectin of the present invention preferably has a viscosity from about 1 to 15 cPs, and more preferably from about 2 to 7 cPs.
The low methoxyl pectin of the present invention can be a powder form or an aqueous form having a pH from about 2 to 6.
The degree of amidation of the low methoxyl pectin of the present invention is preferably from about 1 to 30%, and more preferably from about 4 to 21%.
The degree of esterification of the low methoxyl pectin of the present invention is preferably from about 30 to 55%, and more preferably from about 40 to 52%.
As discussed above, the present invention is directed to a process for preparing a low methoxyl pectin displaying pseudoplasticity and substantially no phase separation in an aqueous solution comprising at least one polyvalent cation which comprises treating a pectin starting material having a degree of esterification of greater than about 60% to obtain at least a non-calcium sensitive pectin fraction.
The process of the present invention is prepared by (a) treating a pectin starting material having a degree of esterification of greater than about 60% with a cation-containing preparation to obtain at least a non-calcium sensitive pectin fraction and a calcium sensitive pectin fraction; (b) separating the non-calcium sensitive pectin fraction from the calcium sensitive pectin fraction; and (c) deesterifying or deesterifying and amidating the non-calcium sensitive pectin fraction to obtain the low methoxyl pectin.
Alternatively, the non-calcium sensitive pectin is prepared by (a) treating a pectin starting material having a degree of esterification of greater than about 60% with an enzyme to obtain the non-calcium sensitive pectin fraction; or (b) reesterifying the calcium sensitive pectin fraction to obtain the non-calcium sensitive pectin fraction.
The pectin starting material has a degree of esterification which is at least about 60%, and more preferably at least about 70%.
The pectin starting material is obtained from at least one of citrus peels, apple juices, apple ciders, apple pomace, sugar beets, sunflower heads, vegetables or waste products from plants selected from at least one of apples, sugar beet, sunflower and citrus fruits, and more preferably from at least one of limes, lemons, grapefruits, and oranges.
The process of the present invention is prepared by deesterifying or deesterifying and amidating a non-calcium sensitive pectin to obtain the low methoxyl pectin.
The non-calcium sensitive pectin is deesterified with an acid in a random fashion to obtain the low methoxyl pectin. The acid is at least one of nitric, hydrochloric, and sulfuric. The degree esterification of the low methoxyl pectin is from about 20 to 55%, and more preferably from about 24 to 40%.
The process of the present invention can be prepared by deesterifying and amidating a non-calcium sensitive pectin with a base in a random fashion to obtain the low methoxyl pectin. The base is at least one of sodium hydroxide and ammonia.
The degree of esterification that is at least about 1% and at most about 15% higher than the degree of esterification of the starting material, and more preferably at least about 7% and at most about 15% higher than the degree of esterification of the starting material.
As discussed above, the present invention is directed to a process for stabilizing particulates in an aqueous system which comprises adding a low methoxyl pectin to an aqueous system containing suitable concentration of polyvalent cations, wherein said low methoxyl pectin displays pseudoplasticity and substantially no phase separation in an aqueous solution comprising at least one polyvalent cation. The process further comprises adding a food, or cosmetic or pharmaceutical product to the aqueous system.
Also as discussed above, the present invention is directed to a stabilizing particles in aqueous system containing a low methoxyl pectin that displays pseudoplasticity and substantially no phase separation. The pH of the aqueous system is from about 2.5 to 5, and more preferably from about 3 to 5.
The aqueous system of the present invention can comprise at least one of food product, cosmetic product, and pharmaceutical product.
Accordingly, it would be desirable to be able to provide pectin for use in suspending particulates in aqueous systems that: (1) has high, low shear viscosity, i.e., displays shear thinning (pseudoplastic) properties; (2) has shear thinning properties with acceptable mouth-feel; (3) displays significantly reduced syneresis and/or phase separation in the presence of relatively high levels of calcium and over long storage periods; and (4) undergoes minimal changes in rheology during long term storage.